The present invention relates to a piston compressor with a lubrication mechanism, which includes a rotary valve rotated integrally with a rotary shaft and having a supply passage for introducing refrigerant from suction-pressure region of the compressor into a compression chamber defined in a cylinder bore by a piston.
A conventional piston type compressor using a rotary valve is disclosed in Japanese Unexamined Patent Application Publication No. 2003-247488. The compressor has a double-headed piston accommodated in paired front and rear cylinder bores of front and rear cylinder blocks, respectively. The piston forms compression chambers in the respective front and rear cylinder bores. The piston is reciprocated in the paired cylinder bores with the rotation of a swash plate rotating integrally with a rotary shaft of the compressor.
The rotary shaft is formed integrally with front and rear rotary valves. The rotary shaft has an in-shaft passage formed therein. The in-shaft passage has two outlets that form a part of the respective front and rear rotary valves. Each of the front and rear cylinder blocks is formed with suction ports that communicate with the respective compression chambers. The outlets of the in-shaft passage are intermittently communicable with the associated suction ports, with the rotation of the rotary shaft, that is, the rotation of the rotary valve. When the outlet of the in-shaft passage communicates with the suction port, refrigerant in the in-shaft passage is introduced into the compression chamber.
The in-shaft passage communicates with a suction chamber that is formed in a rear housing of the compressor. Refrigerant in the suction chamber is introduced through the in-shaft passage into the compression chambers in the respective front and rear cylinder bores. Refrigerant in the compression chamber of the front cylinder bore is discharged into a discharge chamber formed in a front housing of the compressor while pushing open a discharge valve. Refrigerant in the compression chamber of the rear cylinder bore is discharged into a discharge chamber formed in the rear housing while pushing open a discharge valve.
The compressor has a front thrust bearing interposed between the swash plate and the front cylinder block, and a rear thrust bearing interposed between the swash plate and the rear cylinder block. The position of the swash plate is restricted between the front and rear cylinder blocks by the front and rear thrust bearings.
The rotary shaft has an oil hole and a pressure-relief hole formed therein, and these holes extend between the outer peripheral surface of the rotary shaft and the in-shaft passage. The in-shaft passage includes a small-diameter portion and a large-diameter portion on the front and rear sides thereof, respectively. The in-shaft passage further includes a step located at the boundary between the small diameter portion and the large diameter portion and facing the rear thrust bearing. The oil hole is located upstream of the step as viewed in refrigerant flowing direction, in facing relation to the rear thrust bearing. The pressure relief-hole is located at a position facing the front thrust bearing.
Part of refrigerant flowing into the in-shaft passage from the suction chamber impinges on the step, so that lubricating oil contained in the refrigerant is separated. Part of such lubricating oil is delivered through the oil hole into the rear thrust bearing by centrifugal force caused by the rotation of the rotary shaft, so that the rear thrust bearing is lubricated. When the pressure of the crank chamber accommodating therein the swash plate is increased, refrigerant existing in the crank chamber is delivered through the pressure-relief hole into the in-shaft passage, so that the front thrust bearing is lubricated by lubricating oil contained in such refrigerant.
In the above-described compressor, however, since flow path extending through the front thrust bearing and the pressure-relief hole is straight, lubricating oil contained in the refrigerant flowing in such flow path is not separated sufficiently. Therefore, the lubrication of the front thrust bearing located adjacent to the pressure-relief hole may not be sufficient.
The present invention is directed to an improved lubrication of a thrust bearing in a piston compressor.